For cooling an engine of a construction machine, an industrial vehicle and so forth, it has been conventional to circulate a coolant for the engine to a radiator, and in conjunction therewith, to blow an air to the radiator by means of a cooling fan.
The foregoing cooling fan is mechanically driven by the engine, or, in the alternative, by a hydraulic motor which is rotated by a discharged pressurized fluid of a hydraulic pump driven by the engine.
Since the conventional cooling fan is driven by utilizing a horse power of the engine, the horse power of the engine is consumed for driving the cooling fan.
Therefore, the present invention is worked out for solving the problem set forth above, and has an object to provide a drive system of a cooling fan.